There is no special diet needed for weight training, especially for a teenager. The special diets, which are high on protein, are for people who want to get very large muscles, but that's different from weight training. Those diets are also unhealthy, as too much protein strains the kidneys and the supplements and shakes and all that contain a lot of harmful ingredients and produce a dietary imbalance. Better you learn to eat a healthy diet, high in antioxidant rich vegetables and essential fats with the proper balance of good carbs and protein and worry more about strength from the weight training than how you look. And look to your flexibility -- huge muscles are nice for those who like them, but they can interfere with movement. Train to be fit, not to be huge, if you want to be healthy.
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you just really need to watch the amount of carbs and sugars you eat. you really can eat whatever you want just don't go over the top.